Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Third Baby Sickened With Bacteria Sometimes Tied to Formula

An infant in Oklahoma is the third reported case of illness tied to a rare bacterium that has been linked in the past to tainted baby formula, the Associated Press reported Wednesday.

Infection with the bacterium, Cronobacter sakazakaii, is thought to have killed a 10-day-old infant in Missouri. A second child, from Illnios, was sickened but has since recovered, the AP said.

The latest case involves an infant in Tulsa County, Okla., who fell ill but has also rebounded. Cases of C. sakazakaii infection have been linked in the past to contaminated formula, and Enfamil was initially suspected as a route of infection in the Missouri death. The child in Oklahoma had not consumed Enfamil, the U.S. Centers for Disease Control and Prevention said.

Officials at the CDC said they are still awaiting results of tests of the formula and the distilled water used in preparing it, and they stressed that the three cases may not be related.

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Clot After Long Flight May Have Killed Rapper Heavy D

The Los Angeles County coroner's office says that the death last month of rap musician Heavy D at age 44 was caused by a clot in his lung that likely formed during a long flight from London to L.A., the Los Angeles Times reports.

The condition, formally called pulmonary embolism, can arise when a clot forms in the legs during long periods of inactivity. The clot can then travel to the lungs where it can prove lethal if not treated right away.

The rap star, whose real name was Dwight Arrington Myers, collapsed outside his home in Beverly Hills on Nov. 8 and died later at Cedars-Sinai Medical Center.

Speaking with the Times, Dr. Matthew Butteri, an internist at UC Irvine Medical Center, said a pulmonary embolism is "the equivalent of a heart attack. Just like when you have a blockage in your coronary arteries and you have a heart attack. Well, this is an infraction in your lungs, so it's really a lung attack because the blood clot is preventing getting oxygen to critical lung tissue." He recommended that people take short walks or perform in-flight exercises while on long-haul flights, to reduce their risk.

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No Link Between HPV Vaccine, Promiscuity for Girls: Study

A new survey appears to discount the notion that receiving a vaccine against the human papillomavirus (HPV) will raise rates of promiscuity among girls aged 15 to 19.

The vaccine is meant to counter strains of sexually transmitted HPV that are thought to be responsible for most cases of cervical cancer. But some have worried that the shot might encourage young girls to become sexually active.

The new survey, published in the January issue of The American Journal of Preventive Medicine, found no such link, The New York Times reported. The study also found that sexually active girls who'd received the shot were also more likely to consistently use condoms compared to unvaccinated sexually active girls.

"This is all preliminary data, but it shows no association between HPV vaccination and sexual risk," lead author Nicole C. Liddon of the U.S. Centers for Disease Control and Prevention told the Times. "So it should to some degree assuage any concerns that HPV vaccination would lead to increased sexual activity," she said.

According to the report, by the end of 2008, 30 percent of females ages 15 to 19, and 16 percent of females ages 20 to 24 had gotten at least one dose of the HPV vaccine.

2nd Study Linking Retrovirus to Chronic Fatigue Syndrome Is Retracted

Yet another study linking retroviral infections to chronic fatigue syndrome has been called into question, with the findings of a 2010 study retracted on Monday.

Last week, a study published in Science a year earlier was retracted by the editors of that journal. That research found a possible association between the illness and a mouse leukemia retrovirus known as XMRV. This second study, published in the Proceedings of the National Academy of Sciences, was withdrawn by its authors, according to The New York Times.

Although the 2010 study had confirmed the findings of the 2009 research, other scientists had been unable to arrive at the same conclusion. Some had said that laboratory materials were contaminated during the course of their work.

Respected researchers from the U.S. Food and Drug Administration, the U.S. National Institutes of Health (NIH) and Harvard Medical School were all involved in the 2010 study. Randy Schekman, former editor-in-chief of PNAS, told the Times that the journal had been "encouraging" the authors to reconsider their findings in light of subsequent research.

In the retraction, the authors wrote, "It is our current view that the association of murine gamma retroviruses with [chronic fatigue syndrome] has not withstood the test of time or of independent verification and that this association is now tenuous."

Meanwhile, results expected in March from a large-scale NIH study should help decide definitively whether chronic fatigue syndrome is related to these retroviruses, the Times reported.